What is the reason for a black patch in the middle of tongue coating?

Black tongue is a hair-like damage caused by excessive elongation and shedding of filiform nipples on the back of the tongue. The cause is generally related to poor oral hygiene, excessive smoking, prolonged use of antibiotics, candida infection on the surface of the tongue, eating foods containing pigments, etc. There are generally no other symptoms, and the course of disease is slow and has no effect on health. Treatment for black tongue includes: First, to improve oral hygiene, pause or replace topical drugs, stop eating pigmented foods. Second, brush the tongue area with a toothbrush. Third, fungal infections can be smeared with nystatin.